The present invention relates to an air filter for a well,  and, more particularly, to an air filter assembly installed within the well casing of a well to prevent air borne  airborne contaminants from entering the well. The air filter assembly of the present invention is preferably designed for application in water wells, but may be applied to other systems such as oil wells, natural gas wells, gasoline fuel dispensing systems and monitoring wells. The air filter assembly of the present invention is designed to prevent pollutants from contaminating a well.
A typical water well is established by first drilling a hole in the ground in search of water from a water bearing aquifer. Once water is reached by the drill, a well casing is inserted into the bore hole to preserve the sides of the well. The well casing is typically a steel or plastic pipe installed while drilling a well, to prevent collapse of the well bore hole and to allow placement of a submersible pump and other equipment. The well casing typically extends several inches above the ground. A submersible pump is inserted into the well below the water level to pump water from the aquifer. One end of a drop pipe is attached to the submersible pump to draw water out of the well. The other end of the drop pipe is attached to a discharge pipe for carrying water to a pressure tank for distribution and use.
To prevent contaminants from entering the well and to protect the inside of the casing and the well, a well cap may be installed on top of the well casing extending above the ground. The well cap is used to cover the top of the well casing pipe and thereby seal the top of the well casing to prevent the entry of contaminants in the well. The well cap is generally used in systems where the discharge pipe for distributing and supplying water is underground. The well cap also typically includes a conduit box for routing electrical wires from the submersible pump to an electrical power source. The well cap is typically not airtight, and therefore allows air to enter the well around openings between the well cap and the top of the well casing. This opening allows air to flow in and out of the well during pressure changes. In addition to the well cap, a wire screen may be attached to the top of the well casing to prevent large objects from contaminating the well.
As an alternative to the well cap, a well seal may also be used to cover the top of the well casing. The well seal includes a gasket that seals the top of the well casing to prevent entry of contaminants in the well. The well seal is generally used in systems where the discharge pipe for distributing and supplying water comes up through the top of the well casing. The well seal also typically includes openings for a screened vent pipe and a conduit box to pass through the gasket. The screened vent pipe allows air to enter and exit the well during pressure changes. The conduit box is used for routing electrical wires from the submersible pump to an electrical power source. The well seal provides a seal around the discharge pipe, vent pipe and conduit box. However, air enters the well through the vent pipe. The vent pipe screen functions to reduce contaminant entry into the well by preventing large objects from entering the well.
During use, the submersible pump pulls air into the well. The air may include dirt, dust, bacteria, gaseous chemicals, volatile organic compounds (VOCs), insects and other air born  airborne contaminants that may contaminate the well and should be removed. When the pump stops, a change in pressure forces air out of the well. In addition, the normal changes in atmospheric pressure cause air to flow in and out of the well. There is nothing in the prior art to remove air born  airborne contaminants from entering a well and possibly contaminating the water in the well. The well cap and well seal do not prevent dirt, dust, bacteria, gaseous chemicals, VOCs and other air born  airborne contaminants from entering the well and possibly contaminating the water.
Accordingly, there is a need for an air filter for a well. The air filter being  is installed within the well casing of the well or attached to the side of the well casing for preventing air borne contaminants from entering the well. The air filter of the present invention removes dirt, dust, bacteria, gaseous chemicals and VOCs from the air, and stops insects from entering the well.